Agelasines O–U, new diterpene alkaloids with a 9-N-methyladenine unit from a marine sponge Agelas sp.

New diterpene alkaloids, agelasines O–U (1–7), have been isolated from an Okinawan marine sponge Agelas sp. The gloss structures and relative stereochemistries of 1–7 were elucidated from the spectroscopic data. Agelasines O–R (1–4) were the third examples of diterpene alkaloid with a 9-N-methyladenine and a pyrrole units. Agelasine O (1) has a halimane skeleton, while agelasines P–R (2–4) have a clerodane skeleton. Agelasines S–U (5–7) were new diterpene alkaloids with a 9-N-methyladenine unit consisting of a halimane skeleton, a labdane skeleton, and a clerodane skeleton, respectively. Agelasines O–R (1–4) and T (6) showed antimicrobial activities against several bacteria and fungi.